In a driving tool of combustion type, for example, a combustion type nail driving machine, a combustion chamber frame is provided in a housing thereof. When the combustion chamber frame is pushed upward, the combustion chamber frame is pressed to a head cap which is positioned above the combustion chamber frame, whereby a combustion chamber is formed in a space defined between the combustion chamber frame and the head cap. A driving power for striking a nail is obtained, by burning combustible gas inside this combustion chamber.
As disclosed in Patent Documents 1 to 3, the combustion chamber frame is pushed upward by pushing a push lever which is connected to the combustion chamber frame. Specifically, the push lever is provided in a nose part which is arranged at an end of the housing positioned below the combustion chamber frame and supports a nail to be driven out, and when the nose part is brought into contact with a driven member, the push lever is also brought into contact with the driven member simultaneously, whereby the combustion chamber frame which moves in association with the push lever is pushed upward.
In some cases, the driving tool is used for attaching a connection metal to a wood, for example. In this case, it is necessary to drive a fastening piece such as a nail into the wood through a hole formed in the connection metal, and therefore, a driving position must be accurately restricted.
As means for performing accurate driving, such a structure that besides a piston for driving the nail, a sub piston is provided to protrude a distal end portion of the nail for enhancing visibility, as disclosed in Patent Document 4, and such a structure that the nail is driven into a position where the push lever is in contact with the driven member, as disclosed in Patent Document 5 are publicly known.
[Patent Document 1]
Japanese Patent Publication No. JP-B-H01-34753
[Patent Document 2]
Japanese Patent Publication No. JP-B-H03-25307
[Patent Document 3]
Japanese Patent Publication No. JP-B-H04-11337
[Patent Document 4]
Japanese Patent Publication No. JP-B-H07-53907U
[Patent Document 5]
Japanese Patent Publication No. JP-A-H08-52666